Get visual transform of object through python
As your mesh is composed of multiple pieces that are posed with armature, the mesh itself has only 1 origin and 1 matrix transform.

To get the transformation of pieces you need to extract transformation of those pose bones.

You can use bpy.data.objects["Armature"].pose.bones["Bone"].matrix added to your armature global transform matrix or also you can use this answer:

How can I manually calculate bpy.types.PoseBone.matrix